This application relates generally to bearing assemblies and, more particularly, to lubrication systems for bearing assemblies.
As turbine engines have evolved, higher stage loading turbo-machinery, including larger bearing assemblies and rotor shafts, have been included within the engines to provide increased pressure ratio cycles for the turbine engines. Higher pressure ratios increase cycle temperatures and air temperatures within the engine. Specifically, higher stage loading causes an operating speed of the turbines to increase, resulting in temperature increases in the rotor and bearing assemblies.
To minimize the effects of increased pressure ratio cycles, known bearing assemblies include lubrication systems that attempt to lubricate the bearing assemblies supporting rotor shafts to reduce wear to the bearing assemblies. The bearing assemblies include a split inner race mounted to a rotor shaft, an outer race, and a bearing element supported therebetween. The lubrication system includes an oil jet to supply oil to the underside of a shaft and a plurality of axial grooves for supplying oil to the bearing assembly. To structurally and physically accommodate the larger diameter areas, the bearing assemblies are often fabricated with larger components.
Other know bearing assemblies include a plurality of blades, the oil scoop, that capture oil and direct it radially, then locally axially to a plurality of axial slots. To ensure each axial slot to be filled receives an adequate amount of oil, the ring has enough axial width for the oil to flow circumferentially and fill the ring fully prior to reaching the axial distribution slot. As a result, all axial slots receive equal amounts of oil.
In cases where there is not adequate axial width of the oil distribution rings, the axial grooves nearest the oil inlet will preferentially collect and transport the oil. As a result, often such lubrication systems do not provide an even distribution to radial grooves that channel the oil to the bearing assemblies and thus, the bearing S assemblies do not receive adequate or complete lubrication. Over time, continued ineffective lubrication may result in increased bearing wear, thus decreasing a useful life of the bearings.
In an exemplary embodiment, a gas turbine engine includes a lubrication system that supplies oil through a plurality of circumferential grooves and a plurality of axial grooves to a bearing assembly. The circumferential and axial grooves extend within an inner surface of a first rotor shaft that is sized to fit with an interference fit around a main rotor shaft. The circumferential grooves are spaced circumferentially around the inner surface of the first rotor shaft and are substantially perpendicular to the axial grooves. The circumferential grooves are in flow communication with a plurality of scoops that extend between an outer surface of the first rotor shaft and the first rotor shaft inner surface. The axial grooves extend from the circumferential grooves and are in flow communication with the bearing assembly.
During operation, lubricating oil supplied to the first rotor shaft is directed radially inward through the rotor shaft scoops. The oil is channeled through the scoops into the plurality of first grooves. The oil then flows circumferentially through the first groove and is dispersed into the plurality of axial grooves to be channeled to the bearing assembly. Because the first groove permits the lubricating oil to initially flow circumferentially, the oil is more evenly distributed to each of the axial grooves. As a result, a bearing assembly is provided that receives an enhanced and even distribution of lubricating oil such that bearing wear is reduced and bearing useful life is extended.